Belt-conveyance control device, image forming apparatus, belt-conveyance control method, and computer program product

Abstract

A control unit calculates a difference between a displacement of a belt detected by an encoder and a predetermined target value, calculates a pulse frequency of a driving pulse signal based on a feedback control based on the difference and a feed-forward control based on a reference driving pulse frequency, sets a control range of the feedback control to be equal to or smaller than a frequency of one rotation of a driven roller, and controls driving of a pulse motor such that the belt moves at a constant speed.

1. A belt-conveyance control device that includes a belt that is supported by a drive roller and a driven roller, a pulse motor that drives the drive roller, and a first encoder that is attached to the driven roller to detect an angular displacement of the driven roller, the belt-conveyance control device controlling a conveying speed of the belt, the belt-conveyance control device comprising:
 a control unit that
 calculates a difference between the angular displacement detected by the first encoder and a predetermined reference displacement value of the driven roller, 
 calculates a pulse frequency of a driving pulse signal for driving the pulse motor based on a feedback control based on the calculated difference and a feed-forward control based on a reference driving pulse frequency, 
 sets a control range of the feedback control to be smaller than a frequency of one rotation of the driven roller, and 
 controls driving of the pulse motor such that the belt moves at a constant speed. 
 
 
     
     
       2. The belt-conveyance control device according to  claim 1 , wherein a transmission system from the pulse motor to the drive roller is a transmission system in which the angular displacement of the driven roller is lower than one rotation of the driven roller. 
     
     
       3. The belt-conveyance control device according to  claim 1 , wherein a diameter of the drive roller is larger than that of the driven roller. 
     
     
       4. The belt-conveyance control device according to  claim 1 , wherein the control unit adds a target pulse frequency for cancelling a fluctuation component associated with the drive roller in a transmission system from the pulse motor to the drive roller. 
     
     
       5. The belt-conveyance control device according to  claim 1 , further comprising:
 a second encoder that is attached to the drive roller to detect a fluctuation component in the transmission system, wherein 
 the control unit generates the reference driving pulse frequency based on the fluctuation component in the transmission system measured by the second encoder. 
 
     
     
       6. The belt-conveyance control device according to  claim 1 , wherein the control unit causes at least one of a rotation frequency of a transmission system from the pulse motor to the drive roller and a rotation frequency of the drive roller to be different from a rotation frequency of the driven roller by one rotation, and adds to the reference driving pulse frequency a target pulse frequency that is generated based on a result of measurement by the first encoder with respect to a fluctuation component of at least one of the transmission system and the drive roller whose rotation frequency is made different from that of the driven roller by one rotation. 
     
     
       7. The belt-conveyance control device according to  claim 6 , wherein the control unit sets at least one of the rotation frequency of the transmission system and the rotation frequency of the drive roller in one rotation to be lower than the rotation frequency of the driven roller in one rotation. 
     
     
       8. An image forming apparatus comprising the belt-conveyance control device according to  claim 1 . 
     
     
       9. The image forming apparatus according to  claim 8 , wherein the belt is a photosensitive belt. 
     
     
       10. The image forming apparatus according to  claim 8 , wherein the belt is an intermediate transfer belt. 
     
     
       11. The image forming apparatus according to  claim 10 , further comprising:
 a plurality of photosensitive elements that transfers images with different colors onto the intermediate transfer belt, wherein 
 a perimeter of each of the drive roller and the driven roller is approximately equal to an interval between the photosensitive elements. 
 
     
     
       12. The image forming apparatus according to  claim 8 , wherein the belt is a sheet conveying belt. 
     
     
       13. A method of controlling a conveying speed of a belt in a belt-conveyance control device that includes the belt that is supported by a drive roller and a driven roller, a pulse motor that drives the drive roller, and an encoder that is attached to the driven roller to detect an angular displacement of the driven roller, the method comprising:
 calculating a difference between the angular displacement detected by the encoder and a predetermined displacement reference value of the driven roller; 
 calculating a pulse frequency of a driving pulse signal for driving the pulse motor based on a feedback control based on the difference and a feed-forward control based on a reference driving pulse frequency; 
 setting a control range of the feedback control to be smaller than a frequency of one rotation of the driven roller; and 
 controlling driving of the pulse motor such that the belt moves at a constant speed. 
 
     
     
       14. The method according to  claim 13 , wherein the controlling includes adding a target pulse frequency for cancelling a fluctuation component associated with the drive roller in a transmission system from the pulse motor to the drive roller. 
     
     
       15. The method according to  claim 13 , wherein the controlling includes
 causing at least one of a rotation frequency of a transmission system from the pulse motor to the drive roller and a rotation frequency of the drive roller to be different from a rotation frequency of the driven roller by one rotation, and 
 adding to the reference driving pulse frequency a target pulse frequency that is generated based on a result of measurement by the encoder with respect to a fluctuation component of at least one of the transmission system and the drive roller whose rotation frequency is made different from that of the driven roller by one rotation. 
 
     
     
       16. The method according to  claim 13 , wherein the belt is a photosensitive belt. 
     
     
       17. The method according to  claim 13 , wherein the belt is an intermediate transfer belt. 
     
     
       18. The method according to  claim 13 , wherein the belt is a sheet conveying belt. 
     
     
       19. A computer program product comprising a non-transitory computer-usable medium having computer-readable program codes embodied in the medium for controlling a conveying speed of a belt in a belt-conveyance control device that includes the belt that is supported by a drive roller and a driven roller, a pulse motor that drives the drive roller, and an encoder that is attached to the driven roller to detect an angular displacement of the driven roller, the program codes when executed causing a computer to execute:
 calculating a difference between the angular displacement detected by the encoder and a predetermined displacement reference value of the driven roller; 
 calculating a pulse frequency of a driving pulse signal for driving the pulse motor based on a feedback control based on the calculated difference and a feed-forward control based on a reference driving pulse frequency; 
 setting a control range of the feedback control to be smaller than a frequency of one rotation of the driven roller; and 
 controlling driving of the pulse motor such that the belt moves at a constant speed. 
 
     
     
       20. The computer program product according to  claim 19 , wherein the controlling includes adding a target pulse frequency for cancelling a fluctuation component associated with the drive roller in a transmission system from the pulse motor to the drive roller.